Electric field control element for phonons

ABSTRACT

Generally discussed herein are techniques for and systems and apparatuses configured to control phonons using an electric field. In one or more embodiments, an apparatus can include electrical contacts, two quantum dots embedded in a semiconductor such that when an electrical bias is applied to the electrical contacts, the electric field produced by the electrical bias is substantially parallel to an axis through the two quantum dots, and a phononic wave guide coupled to the semiconductor, the phononic wave guide configured to transport phonons therethrough.

CLAIM OF PRIORITY

This patent application claims the benefit of priority of U.S.Provisional Patent Application Ser. No. 61/934,532, filed on Jan. 31,2014, which is hereby incorporated by reference herein in its entirety.

GOVERNMENT RIGHTS

This invention was made with government support under Grant No. 0832819awarded by the National Science Foundation. The government has certainrights in the invention.

BACKGROUND

Phonons, quantized vibrations of an elastic structure, permeate thecrystalline components of modern technology, and are central to theemerging research area termed “phononics”. Associated with heat lostenergy and noise, phonons are encountered as such in many electronicdevices used in daily life. Phonons are considered to govern fundamentalphenomena on the quantum level, such as relaxation dynamics innanostructures to superconductivity. In the development of solid statequantum technologies phonons are mainly considered for the limitationsthey impose.

BRIEF DESCRIPTION OF DRAWINGS

Various ones of the appended drawings illustrate embodiments of thesubject matter presented herein. The appended drawings are provided toallow a person of ordinary skill in the art to understand the conceptsdisclosed herein, and therefore cannot be considered as limiting a scopeof the disclosed subject matter.

FIG. 1 shows an example of a transition state diagram for a pair ofzero-dimensional structures.

FIG. 2 shows a block diagram of an example of a device configured tocontrol generation or destruction of a phonon.

FIG. 3 shows an example of a Schottky diode configured to controlgeneration or destruction of a phonon.

FIGS. 4A, 4B, and 4C show examples of an energy level band diagram of amedium and zero-dimensional structure pair.

FIG. 5 shows an example of a line graph of energy vs. electric field fora neutral exciton.

FIG. 6 shows an example of a state diagram of a medium and quantum dotpair.

FIG. 7 shows an example of a phonon transistor that includes a pair ofzero-dimensional structures.

FIG. 8 shows an example of a scatter plot and line graph of phononintensity at the drain of the transistor of FIG. 7 vs. the voltage atthe gate of the transistor.

FIGS. 9A and 9B show a plurality of scatter plots of phonon intensity atthe drain of the transistor of FIG. 7 vs. the voltage at the gate of thetransistor.

FIG. 10 shows a flow diagram of an example of a technique for making aphonon control mechanism.

FIG. 11 shows a block diagram of an example of a strain or motionsensor.

DETAILED DESCRIPTION

The description that follows includes illustrative apparatuses, systems,methods, and techniques that embody various aspects of the subjectmatter described herein. In the following description, for purposes ofexplanation, numerous specific details are set forth to provide anunderstanding of various embodiments of the subject matter. It will beevident, however, to those skilled in the art that embodiments of thesubject matter may be practiced without at least some of these specificdetails.

This disclosure relates generally to the field of phonon control andmore specifically to systems, apparatuses, and methods related to acontrol mechanism for phonons.

Omnipresent electron-phonon interactions and the predominantlydissipative nature of phonons are a major source of decoherence of theatom-like quantum state hosted by low-dimensional solid statestructures, such as zero-dimensional structures like quantum dots (QDs).In contrast, conditions in which phonons can be made non-dissipative orcoherent are discussed herein. A result is a variety of controlmechanisms (e.g., field-effect transistors) that can control phonons(“phonon FETs”). The phonon FETs can be implemented in a conventionalintegrated circuit device architecture individually or in combination.

Discussed herein is a tool that can control the generation or flow of aphonon. Like a field-effect transistor (FET) controls the flow ofelectrons or electricity (“electric FET”), apparatuses and systemsdiscussed herein can control the flow of conductive heat (a phonon) viaan electric field produced using an electric potential or electricalbias (e.g., a voltage). The physical structure of the phonon FET caninclude a pair of quantum dots embedded in a conventional semiconductormaterial or device (e.g., a Schottky diode, capacitor, a PIN-diode, orother semiconductor technology). A Schottky diode and a simplecapacitor-like structure (see FIG. 2) are described herein, however, thedisclosure can be used in a variety of semiconductor and other electricor electronic devices. An electric bias can be applied so as to createan electric field along or substantially parallel to an axis through orconnecting the dot pair. Phonons can pass through the pair of quantumdots on two paths, such as to cause interference between phonons on eachpath. Depending on the electric bias applied, this interference can beconstructive (phonon flow is enabled or enhanced) or destructive (phononflow is inhibited or blocked). This structure can perform the functionof a phonon switch that is based on the applied electric bias (i.e. theelectric field that is produced by applying the electric bias). Afundamental principle that governs the phonon interaction is a Fano-typequantum interference that creates a resonant polaron, which in this caseis a molecular polaron.

An advantage of the phonon FET can include an increased energyefficiency. Another advantage of the phonon FET can include the abilityto make use of a phonon rather than to let it go to waste as heat, suchas in a conventional integrated circuit or other semiconductortechnology. For example, the controlled phonon can be representative ofdata where a presence or absence of the phonon indicates a bit of “1” or“0” so as to perform a function similar to that of an electron in acurrent electronic system, thus supplanting the electron orsupplementing the information provided by the electron.

The phonon control mechanism (e.g., phonon FET) can be used to controlthe flow of phonon heat so as to increase an efficiency in which heat isdissipated or increased or to more precisely direct a flow of heat. Thephonon control mechanism can be used as an interface between photoniclogic (light based, for example fiber optic), electronic logic (electronbased logic), phononic logic (phonon based logic), or spintronics (spinbased logic). The phonon control mechanism can be used in quantuminformation technologies (e.g., for revealing coherent coupling betweenquantum structures). The phonon control mechanism can be used as a logicelement in an information system (e.g., a solid state based informationsystem) or processing technology, such as by using the phonon controlmechanism as a logic switch. The phonon control mechanism can reducenoise caused by a phonon and can be used in an application to exploitits noise reducing ability, such as in a sensor or detector technology(e.g., light or TeraHertz radiation detector). Yet another applicationof the phonon control mechanism is in the field of solar technologywhere a high light absorption and reduced thermal emmittance can beadvantageous, such as can be provided by the phonon control mechanism.The phonon control mechanism can be used in a strain or motion sensor,such as is discussed in more detail herein.

Reference will now be made to the FIGS. to describe further details ofapparatuses and systems and techniques (e.g., methods) that can includea phonon control mechanism.

FIG. 1 shows a block diagram of a state diagram 100 of a phonon. Thephonons can begin in a medium (e.g., a solid, liquid, or gas) that is aninitial state 102. From the initial state 102 the medium can transitionthrough a discrete state 104 or a continuum state 106 to a final state108.

Some mechanism (the mechanism is not shown in FIG. 1) can generate anenergy that causes a phonon to be produced in a semiconductor ordielectric material of a device that is in the initial state 102. Afterthe phonon has passed through at least a portion of the semiconductor ordielectric material, semiconductor or dielectric material can be in thefinal state 108.

If the medium offers two indistinguishable paths (e.g., one path throughthe discrete state 104 and another path through the continuum state 106)interference can occur. This interference can be constructive, meaning aphonon can be generated (e.g., and emitted) and the final state 108 isreached, or destructive meaning a phonon is not generated or releasedagain and the final state 108 is not reached. The discrete state 104 andthe continuum state 106 can be coupled (e.g., in resonance with eachother), such as through the coupling 110. A medium that offers suchindistinguishable paths can create a “which-path” problem, similar to adouble slit experiment, and can cause Fano-type quantum interference(i.e. a Fano-effect). By controlling the interference of the phonon witha gating mechanism (e.g., an electric field), a phonon transistor can becreated.

FIG. 2 shows an example of a device 200 configured to include a phononcontrol mechanism. The device 200 can include two or morezero-dimensional structures 210A and 210B embedded in a semiconductormaterial 212 (e.g., solid state material) or other electricallyconductive or electrically insulating material. The device 200 caninclude a source lead element 224 and a drain lead element 226. Thedevice 200 can basically be a capacitor with some dielectric orsemiconductor material 212 sandwiched between plates of the capacitor(in this case the contacts 216A and 216B provide the plates of thecapacitor). The semiconductor material 212 can also be a dielectricmaterial which allows an electric field to be generated therein or amaterial that includes a band gap in the presence of an electric field,where different states of the band gap can be reached.

The device 200 can include a gating mechanism through which an electricbias can be applied to the semiconductor material 212. The gatingmechanism shown in FIG. 2 includes two electrically conductive contacts216A and 216B coupled to one or more conductive Input/Output (I/O) pads214A and 214B, respectively. FIG. 2 shows the contacts 216A-216B coupledto the pads 214A-B through an electrically conductive interconnect218A-218B, respectively. In one or more embodiments, an electricalpotential bias can be applied directly to the contact 216A-B rather thanapplying the bias to the I/O pad 214A-B or interconnect 218A-B.

The zero-dimensional structures 210A-B can include a quantum dot or aNitrogen Vacancy (NV) center. The quantum dot can include materialssimilar to or the same as semiconductor material 212. In an embodimentwhere the zero-dimensional structure 210A-B includes an NV center, thesemiconductor material 212 can be diamond. A quantum dot can be on theorder of tens of nanometers or less. A quantum dot is a semiconductorthat has zero or more charges confined in all three spatial dimensions(i.e. length, width, and height), comparable to the extension of thewave function/deBroglie wavelength of the charge, thus, the quantum dotis a zero-dimensional structure. A quantum dot is a nanocrystal,typically including a semiconductor material. A quantum dot isconfigured to exhibit quantum mechanical properties.

The zero-dimensional structures 210A-B can be atom-like structures. Thezero-dimensional structures 210A-B can be embedded, at least partially,in the semiconductor material 212 so as to provide the possibility tocreate a which-path problem for phonons, such as is described withregard to FIG. 1. The zero-dimensional structures 210A-B can representpossible paths through which phonon generation, emission, or destructioncan occur. The semiconductor material 212 together with azero-dimensional structure 210A can provide the continuum state 106, andthe other zero-dimensional structure 210B can provide the discrete state104. In one or more embodiments, the zero-dimensional structure 210Aalone can provide the continuum state 106 and the other zero-dimensionalstructure 210B can provide the discrete state 104.

The zero-dimensional structures 210A-B can be separated by between aboutone and one hundred nanometers. In one or more embodiments, theseparation between the zero-dimensional structures 210A-B can be betweenabout one and thirty nanometers. The separation between thezero-dimensional structures 210A-B can be dependent on the material thezero-dimensional structures 210A-B are fabricated using and whether thezero-dimensional structures 210A-B are side-by-side (e.g., horizontallyadjacent to one another) or on top of each other (e.g., verticallyadjacent to one another). The zero-dimensional structures 210A-B can beseparated by a larger distance if they are side-by-side. This is due, atleast in part, to the processes that can be used to place thezero-dimensional structures 210A-B in the semiconductor material 212. Inthe side-by-side configuration, the zero-dimensional structures 210A-Bcan be placed with a high precision using a site controlled growthtechnique.

The semiconductor material 212 can be a semiconductor that includespositively or negatively doped, undoped, or intrinsic silicon,germanium, carbon, or a combination thereof. The semiconductor material212 can include a compound that includes a compound that is asemiconductor, such as indium arsenide (a compound including indium andarsenic), gallium arsenide (a compound including gallium and arsenic),cadmium selenide, zinc selenide, or other compound semiconductormaterial. The semiconductor material 212 can include cadmium, indium,gallium, nitrogen, phosphorus, antimony, selenium, tellurium, oxygen,sulfur, graphene, diamond, glass, oxide, chlorine, titanium, lead,manganese, nickel, iron, chromium, silicon, silver, platinum, iodine,thallium, bromine, or a combination thereof. The semiconductor material212 can include other semiconductor materials, such as a metal compoundincluding multiple of the additives discussed. Note that an insulator(e.g., dielectric), such as glass, oxide, or diamond, can be used inplace of or in conjunction with the semiconductor material 212.

The contact 216A-B, interconnect 218A-B, or I/O pad 214A-B can include amaterial such as a metal, semiconductor, or other electricallyconductive material.

Different potentials may be supplied to the contacts 216A-B (e.g.,directly to the contacts 216A-B or indirectly to the contacts 216A-B,such as through the I/O pad 214A-B or interconnect 218A-B), such as toprovide an electric potential across the zero-dimensional structures210A-B. An electric field line 222 of an electric field produced throughthe different supplied potentials can be substantially parallel to anaxis 220 through the zero-dimensional structures 210A-B. The electricfield line 222 can be coaxial with the axis 220. Note that FIG. 2depicts the electric field line 222 parallel to and not coaxial with theaxis 220. The electric bias applied to the contact 216 can provide agating mechanism that can prohibit, promote, or inhibit phonongeneration, dissipation, or transport. By varying the electric biasapplied to the contacts 216A-B, constructive or destructive interferencecan be realized. For example, when a first voltage is applied to thecontacts 216A-B, constructive interference between quantum states of thezero-dimensional structures 210A-B (and the semiconductor material 212)can be created and a phonon can be produced. When a second, differentvoltage is applied to the contacts 216A-B, destructive interferencebetween quantum states of the zero-dimensional structures 210A-B can becreated and a phonon can be prevented from being produced, dissipated,or transmitted.

The lead element 224 can include a phonon transport (e.g., heat)element, a photonic transport (e.g., optical) element, an electroniccharge transport element, or a spintronic transport element. The leadelement 224 can be configured to transport an excitation energy to thesemiconductor material 212. The lead element 226 can include a phonontransport element, a photonic transport element, an electronic chargetransport element, or a spintronic transport element. The lead element226 can be configured to transport energy away from the semiconductormaterial 212.

FIG. 3 shows an example of a Schottky diode 300 with a pair of quantumdots including quantum dot material 302A and 302B (e.g.,zero-dimensional structures) embedded therein. Note that FIG. 3 is aspecific implementation of the device 200 of FIG. 2 that is meant toillustrate that the capacitor-like device can be implemented in avariety of devices or structures that are capacitor-like as previouslydescribed. The Schottky diode 300 can be a heterostructure of differentsemiconductor layers and one or more contacts 216A-B. A first contact216A (e.g., the aluminum 314 or titanium 312) of the Schottky diode 300can be fabricated with one or more apertures 316 (e.g., transparent orsemi-transparent apertures) therethrough. The aperture 316 can providean optical access to quantum dots (e.g., quantum dot pairs) or otherportions of the Schottky diode 300, such as to provide excitation energyto the Schottky diode 300. While FIG. 3 shows only one aperture 316,other apertures can be formed through the aluminum 314 or titanium 312layers. In one or more embodiments that include a high resolutionfabrication technique, such as an embodiment including Scanning NearField Optical Microscopy (SNOM) or sight-controlled grownzero-dimensional structures in a photonic waveguide or cavity, theaperture 316 may be unnecessary to provide excitation energy or removephonons (see discussion of FIG. 7 and how the aperture 316 can act as alead element 224 or 226).

The Schottky diode 300 can include a substrate 306. Layers of intrinsicgallium arsenide 304A, 304B, 304C, and 304D can be situated over thesubstrate 306. The layers of intrinsic gallium arsenide 304A-D can beseparated by the quantum dot material 302A-B or a layer of aluminumgallium arsenide 307. The Schottky diode 300 can include a layer oftitanium 312 or one or more layers of aluminum 314 situated over thelayers of intrinsic gallium arsenide 304A-D. The aluminum 314 ortitanium 312 can form a contact 216A-B through which an electric biascan be applied to the Schottky diode 300. The substrate 306 can becoupled to an electric potential, such as a ground, so as to provide anelectric potential difference between the aluminum 314 and the substrate306. The substrate 306 can act as an electrical contact 216A-B. Theelectric potential difference can cause quantum states of the portionsof quantum dot materials 302A-B to couple or resonate.

The quantum dot material 302A-B can be on the order of less than tennanometers thick. In one or more embodiments, the quantum dot materials302A-B can be between about two (2) and three (3) nanometers thick. Inone or more embodiments, the quantum dot materials 302A and 302B can beseparated by about four nanometers. The thickness of the quantum dotmaterials 302A-B can be bigger than three nanometers as long as theyremain zero-dimensional, as discussed herein. The separation between thequantum dot materials 302A-B can be greater or less than four nanometersas previously discussed with regard to separation distance betweenzero-dimensional structures 210A-B.

If a reverse bias (i.e. a voltage configured to increase the depletionregion of the energy band of the semiconductor material) is applied tothe Schottky diode 300, the aluminum 314 and titanium 312 can functionas a first plate of a capacitor, and the doped gallium arsenide 308 canfunction as a second plate of a capacitor, and can generate an electricfield across the region between them. The electric field can couple aquantum state of the quantum dot that includes quantum dot material 302Awith a quantum state of a combination of the quantum dot that includesquantum material 302B and other layers of semiconductor material (e.g.,intrinsic gallium arsenide 304A-D, aluminum gallium arsenide 307, ordoped gallium arsenide 308).

FIGS. 4A, 4B, and 4C show examples of energy level band diagrams 400A,400B, and 400C, respectively, of a medium and quantum dot pair, such asthe semiconductor material 212 and zero dimensional structures 210A-B.The energy level band diagrams 400A, 400B, and 400C include a conductionband edge 404 and a valence band edge 406. The energy level band diagram400A includes electronic states 408A, 408B, 408C, and 408D, and a state410 that includes phonons and is dashed (e.g., a state in which a phononis bound to one or more charges, such as an electron or a hole). Anelectric field caused by a bias applied to the structure 200 can lift orlower the potential on the contact 216B and can keep the potential onthe contact 216A fixed (e.g., grounded or at some other potential). Thepotential difference can cause the valence band edge 406 and conductionband edge 404 to skew, such as shown in FIGS. 4A-C. The skewing canallow for discrete energy levels of the zero-dimensional structure 210Ato be shifted with respect to the energy level of the zero-dimensionalstructure 210B. The two areas where the conduction band edge 404 iscloser to the valence band edge 406 are where the electric field isinteracting with a zero-dimensional structure 210A-B, respectively.

A transition 412A, 412B, or 412C between states of the zero-dimensionalstructures 210A-B can occur when energy is provided to thezero-dimensional structures 210A-B. The transition 412A indicates achange from a state in a valence band energy level of thezero-dimensional structure 210B to a state in a conduction band energylevel of the zero-dimensional structure 210A. The transition 412Bindicates electron or hole tunneling between the zero-dimensionalstructures 210A-B. A phonon can be generated in this transition 412B.The transition 412C indicates a change from a valence band energy levelof the zero-dimensional structure 210A to the conduction band energylevel at state 410 that can include a phonon. At the state 410,tunneling between the zero-dimensional structures 210A-B can occur.

In one or more embodiments, the initial state 102 can correspond to astate where all electrons are in the valence band 406 and no electronsare in the conduction band 404. The continuum state 106 can be enteredwhen an electron transitions from state 408D to state 410. The discretestate 104 can be entered when an electron transitions from state 408A tostate 408E, such as is shown by the transition 412A. The final state 108can be entered when an electron transitions from state 408D to 408E orwhen an electron transitions from state 410 to state 408E, such as byemitting or releasing a phonon. The states 408B-C can be alternativestates for state 408A that are at a different energy. These states408B-C can be accessed by applying a different electric potential to thecontacts 216A-B of the respective device.

In one or more embodiments, the initial state 102 can include emptyzero-dimensional structures 212A-B (neither a hole nor an electron inthe zero-dimensional structure 212A-B), the continuum state 106 caninclude a zero-dimensional structure 212A-B in a polaron state (|X₀,Ω>),the discrete state 104 can include an inter-zero-dimensional structure212-A-B exciton state (a hole in one zero-dimensional structure 210B andan electron in the other zero-dimensional structure 210A), and the finalstate 108 can include a zero-dimensional structure 212A-B exciton stateand a phonon released or unbound to the zero-dimensional structure212A-B.

In one or more embodiments, the initial state 102 can correspond to astate where one or more electrons are in the conduction band 404 and noholes are in the valence band 406. The continuum state 106 can beentered when an electron transitions from state 408D to state 410. Thediscrete state 104 can be entered when an electron transitions fromstate 408A to state 408E, such as shown by the transition 412A. Thefinal state 108 can be entered when an electron transitions from state408D to 408E or when an electron transitions from state 410 to state408E, such as by emitting a phonon.

In one or more embodiments, the initial state 102 can correspond to astate where one or more holes are in the valence band 406 and noelectrons are in the conduction band 404. The continuum state 106 can beentered when an electron transitions from state 408D to state 410. Thediscrete state 104 can be entered when an electron transitions fromstate 408A to state 408E, such as is shown by the transition 412A. Thefinal state 108 can be entered when an electron transitions from state408D to 408E or when an electron transitions from state 410 to state408E, such as by emitting a phonon.

In one or more embodiments, the initial state 102 can include a chargedzero-dimensional structure 212A-B (e.g., a zero-dimensional structure212A-B with one or more holes or electrons therein). The continuum state106 can include a zero-dimensional structure 212A-B in a polaron state(|Ch,Ω>). The discrete state 104 can include an inter-zero-dimensionalstructure 212-A-B charge state (e.g., one of the holes or electrons inone zero-dimensional structure 210B and the remaining holes or electrons(if any) in the other zero-dimensional structure 210A). The final state108 can include a zero-dimensional structure 212A-B charge state and aphonon released or unbound to the zero-dimensional structure 212A-B.

In one or more embodiments, the initial state 102 can correspond to astate where zero or more electrons are in the conduction band 406 andzero or more holes are in the valence band 404. The continuum state 106can be entered when an electron transitions from state 408E to state420, such as by binding a phonon or interacting with an electric field.The discrete state 104 can be entered when an electron transitions fromstate 408E to state 408H, such as is shown by the transition 422A, or anelectron is supplied by an electric lead directly to state 408H. Thefinal state 108 can be entered when an electron transitions from state408H to 408E or when an electron transitions from state 420 to state408E by emitting a phonon. The states 408F-G can be alternative statesfor state 408H that are at different energy. These states 408F-G can beaccessed by applying a different electric potential to the contacts216A-B of the respective device.

In one or more embodiments, the initial state 102 can correspond to astate where zero or more holes are in the valence band 406 and zero ormore electrons are in the conduction band 404. The continuum state 106can be entered when a hole transitions from state 408D to state 430 bybinding a phonon or when a hole is supplied by a lead. The discretestate 104 can be entered when a hole transitions from state 408D tostate 408A, such as is shown by the transition 432A, or a hole isdirectly supplied by an electric lead to state 408A. The final state 108can be entered when a hole transitions from state 408A to 408D or when ahole transitions from state 420 to state 408D, such as by emitting aphonon.

In one or more embodiments, the initial state 102 can include spins inthe zero-dimensional structures 212A-B (e.g., one or more spin polarizedholes or electrons in the zero-dimensional structure 212A-B). Thecontinuum state 106 can include a zero-dimensional structure 212A-B in aspin polarized polaron state (|S,Ω>). The discrete state 104 can includean inter-zero-dimensional structure 212-A-B charge state (e.g., one ofthe spin polarized holes or electrons in one zero-dimensional structure210B and the remaining holes or electrons (if any) in the otherzero-dimensional structure 210A). The final state 108 can include azero-dimensional structure 212A-B spin state and a phonon released orunbound to the zero-dimensional structure 212A-B.

In one or more embodiments, the initial state 102 can correspond to astate where zero or more spin polarized electrons are in the conductionband 406 and zero or more holes are in the valence band 404. Thecontinuum state 106 can be entered when a spin polarized electrontransitions from state 408E to state 420 by binding to a phonon or whenan energy is supplied by a spintronic lead (e.g., the lead element 224).The discrete state 104 can be entered when a spin polarized electrontransitions from state 408E to state 408H, such as is shown by thetransition 422A, or a spin polarized electron is supplied by aspintronic lead element (e.g., a spin injector). The final state 108 canbe entered when a spin polarized electron transitions from state 408H to408E or when an electron transitions from state 420 to state 408E, suchas by emitting a phonon. The states 408F-G can be alternative states forstate 408H that are at different energy. These states 408F-G can beaccessed by applying a different electric potential to the contacts216A-B of the respective device.

In one or more embodiments, the initial state 102 can correspond to astate where zero or more spin polarized holes are in the valence band406 and zero or more electrons are in the conduction band 404. Thecontinuum state 106 can be entered when a spin polarized holetransitions from state 408D to state 430 by binding a phonon or a spinpolarized hole is supplied by a spintronic lead directly to state 430.The discrete state 104 can be entered when a spin polarized holetransitions from state 408D to state 408A, such as is shown by thetransition 432A, or a spin polarized hole is supplied by a spintroniclead directly to state 408A. The final state 108 can be entered when ahole spin transitions from state 408A to 408D or when a spin polarizedhole transitions from state 420 to state 408D by emitting a phonon.

As previously discussed, the initial state 102 can be bypassed, such asby injecting an electron or hole (e.g., a polarized electron or hole)through the lead element 224.

FIG. 5 shows an example of a line graph 500 of energy vs. electric fieldfor a neutral exciton (an electron in the conduction band and a hole inthe valence band). |X₀> represents a ground state exciton where bothcharges are in the zero-dimensional structure 210A. |iX₀> and |iX₁>represent respective exciton states where the hole is in the ground orfirst excited level of the zero-dimensional structure 210A valence band.|X₀,Ω> represents a state in the polaron continuum (e.g., a weakly boundstate formed by a phonon Ω and the zero-dimensional structure's 210Bground state exciton. While this discussion regards optical phonons,acoustic phonons could be used as well. Using an electric field the|iX₀> and |iX₁> states can be tuned in resonance (e.g., coupled) withthe |X₀,Ω> state. If either the |iX₀> or |iX₁> are substantially coupledto |X₀, Ω>, a which-path problem can be created. The coupling can causea resonant or molecular polaron to be formed. The coupling can be causedby quantum mechanical tunneling of charges between the zero-dimensionalstructures 210A-B. The |X₀,Ω>, |iX₀>, and |iX₁>, states can be inducedby an excitation energy, such as electronic, optical, acoustic, orphononic excitation energy. The |CGS> indicates a crystalline groundstate or an unperturbed device 200 state.

FIG. 6 shows an example of a transition diagram 600 between states of amedium and quantum dots, such as the semiconductor material 212 and thezero-dimensional structures 210A-B. The zero-dimensional structure 210Ais represented by the left box of each pair of boxes and thezero-dimensional structure 210B is represented by the right box of eachpair of boxes. A dark dot in the box indicates an electron is present inthe associated zero-dimensional structure 210A-B and a light dotindicates a hole is present in the associated zero-dimensional structure210A-B. Thus, a dark dot in the left box indicates that the electron ispresent in the zero-dimensional structure 210A.

At |i>, which is representative of a crystalline ground state (|cgs>) orthe initial state 102, neither zero-dimensional structure 210A-B mayinclude the electron or hole. At 602A, the state can transition from acgs to a state |d>=|iX_(n)> (e.g., the discrete state 104), where nindicates the energy band level of the zero-dimensional structure210A-B, that includes an indirect exciton (electron and hole in separatezero-dimensional structures 210A-B). The transition at 602A can be thesame as the transition 412A. At 602B, the state can transition from acgs state to a state |c>=|X₀,Ω> (e.g., the continuum state 106), thatincludes a polaron (a phonon and electron and hole in the samezero-dimensional structures 210A-B). The transition at 602B cancorrespond to a charge (e.g., electron or hole) transitioning into thezero-dimensional structure 210A while a phonon is created or bound tothe charge. The transition at 602C can correspond to a holetransitioning into the zero-dimensional structure 210A when a phonon hasbeen released or unbounded. At 602C, tunneling of the electron or holecan occur. This tunneling indicates that the phonon can be preserved inthe structure (e.g., not dissipated or localized) through state|iX_(n)>. The phonon can be released or unbounded at |X₀>. Thetransition at 602C can correspond to the transition 412B. At 602D, thestate can transition from the |d>=|iX_(n)> state to the state |f>=|X₀>(e.g., the final state 108). The transition at 602D can correspond to ahole transitioning from state 408A to the state 408D while a phonon isbeing released or unbound. At 602E, the state can transition from thestate |c>=|X₀,Ω> discrete state 104 to the state |f>=|X₀>. Thetransition at 602E can correspond to a phonon being released or unboundfrom the state 410 taking the zero-dimensional structure 210A-B to thestate 408E. At 602F, the state can transition from |f>=|X₀> to|i>=|cgs>. The transition at 602F can correspond to a transition fromthe state 408E to the state 408D. As used herein “state” refers to thestate of the zero-dimensional structures 210A-B with or without thesemiconductor material 212.

At 602F, a photon can be emitted and the zero-dimensional structures210A-B can return to CGS from state |f>. Detection of the photonemission can provide a means by which to verify phonon generation or alack thereof. The state |f> can be the final state 108, the state |i>can be the initial state 102, the state |c> can be the continuum state106, and the state |d> can be the discrete state 104 (see FIG. 1). Thecoupling 110 between the discrete state 104 and the continuum state 106(e.g., a coherent phonon) can be provided by the tunneling at 602C.

FIG. 7 shows an example of a phonon transistor 700. The phonontransistor 700 can include a gate 702, a source 704, and a drain 706.The gate 702 can include a coupling between the continuum and discretestates (|c> and |d>).

The gate 702 can include the contacts 216A-B, such as to provide astructure through which an electric field can be provided to thezero-dimensional structures 210A-B.

The source 704 can include an uncoupled discrete or continuum state. Thesource 704 can include a lead element 224 coupled to the semiconductormaterial 212. The lead element 224 can be configured to provideexcitation energy, such as from a means for providing excitation energy712 to the semiconductor material 212. The lead element 224 can be anoptical, acoustic, electrical, spintronic, or phononic lead element. Thelead element 224 can be an optical fiber, photonic wave guide, theaperture 316, an electrically conductive wire, or other phononicwaveguide. The lead element 224 can include a heat transfer mechanismconfigured to provide heat energy to the semiconductor material 212. Thelead element 224 can be coupled to the means for providing excitationenergy 712 to the semiconductor 212. The means for providing excitationenergy 712 can include a laser or an electrical power supply. The meansfor providing excitation energy 712 can provide energy to transition thestate from the initial state (|i>) to the discrete state or continuumstate which are either coupled or uncoupled, such as depending on whatbias is applied to the gate 702 and the resulting electric fieldgenerated between contacts 216A and 216B.

The drain 706 can include the final state (|f>) of the zero-dimensionalstructures 210A-B. The drain 706 can include a lead element 226configured to transport a phonon therethrough. The lead element 226 canbe a phononic wave guide or a combination with one or more of aphotonoic waveguide, the aperture 316, an electrically conductive wire,or a spintronic lead element. A phonon emitted through the lead element226 can be determined, at least in part, by the electric bias applied tothe contacts 216A-B or the excitation energy provided through the leadelement 224.

FIG. 8 shows an example of a scatter plot and line graph 800 of phononintensity at the drain 706 versus a voltage applied at the gate 702. Thescatter plot 800 shows a region indicated by the space above dotted line806 and below dotted line 802 where phonon generation can be enhanced(e.g., increased). The space above the dotted line 806 can be whereconstructive interference between quantum states of the zero-dimensionalstructures 210A-B can be produced. The scatter plot 800 shows a regionindicated by the space below dotted line 806 and above the dotted line804 where phonon generation can be suppressed (e.g., decreased). Thespace below the dotted line 806 can be where destructive interferencebetween quantum states of the zero-dimensional structures 210A-B can beproduced. A gating mechanism of a phonon control mechanism (e.g., phonontransistor or phonon FET) can help enhance or suppress the generation ofphonons, such as by changing or controlling the gate voltage or electricbias applied to the contacts 216A-B. The scatter plot 800 shows a regionindicated by the space above dotted line 806 where the source 704 isproducing or generating a phonon, such as an enhanced number or greaternumber of phonons.

FIGS. 9A and 9B show scatter plots 900A and 900B of intensity versusgate voltage. As can be seen, a variety of transistor-like switchingcharacteristics can be achieved by varying the excitation energy, suchas shown in FIG. 9A, or the excitation power density, such as shown inFIG. 9B, at the source 704 or the gate voltage at the gate 702. As usedherein, “intensity” can be the number of phonons that pass through thedrain of the respective phonon control device or mechanism. In thisregard, a high intensity can mean that a high number of phonons isdissipated or pass through the drain 706 (e.g., the lead element 226).

FIG. 10 shows a flow diagram of an example of a technique 1000 formaking a phonon control mechanism. At 1002, a pair of quantum dots canbe arranged within a semiconductor. The quantum dots can be arrangedsuch that quantum states of the pair of quantum dots resonate in thepresence of an electric field. Arranging the two quantum dots caninclude situating a first quantum dot material over a substrate of thesemiconductor so as to form a first quantum dot of the pair of quantumdots and situating a second quantum dot material over the first quantumdot material so as to form a second quantum dot of the pair of quantumdots. The first or second quantum dot material or the intrinsic materialcan include the same materials as the semiconductor material 212 or theadditive. At 1004, a phononic wave guide can be coupled to thesemiconductor.

The technique 1000 can include coupling an optical, electrical, orphononic lead to the semiconductor. The technique can include situatinga layer of intrinsic material over the substrate, wherein the first andsecond quantum dot material are separated by the layer of intrinsicsemiconductor material. The intrinsic semiconductor material canseparate the first and second quantum dot material by less than onehundred nanometers.

FIG. 11 shows a block diagram of an example of a strain or motion sensordevice 1100 that uses phonon properties to determine strain or motionwithin a substrate. Lattice vibrations (represented by the concentricrings 1102) can be coherently tied to the zero-dimensional structures210A-B (tie represented by the arrow 1104) due to a resonance with an|iX> state. Consider the control mechanism 200 that includes a sourcelead element 224 that can provide excitation energy to thezero-dimensional structures 210A-B from a light source. In an unstrained(e.g., unperturbed) substrate, the molecular polaron exists unperturbedfor a certain amount of time, also called the “coherence time”. Thelonger the coherence time, the larger the volume of the substrate themolecular polaron interacts with or senses. Strain in the substratechanges the frequency spectrum of the phonons supported by the material,thus changing the molecular polaron and causing decoherence or ashortened coherence time. The coherence time of a phonon can beincreased by increasing the optical power of the light source.

This effect can be seen by analyzing a phonon-induced transparencysignal (e.g., depth or spectral width of the phonons, such as shown inFIG. 8). Motion or strain in the substrate can then be derived from thetransparency signal. Strain in the substrate can be the result of adefect in the substrate, a deformation (e.g., a bending) of thesubstrate. The deformation can be caused by an accelerationgravitational pull, or in general motion of the substrate. Thus, thephonon control mechanism discussed herein could be used in anaccelerometer, a gradiometer, power sensor, strain gauge, or otherstrain or motion device.

ADDITIONAL NOTES AND EXAMPLES

One or more aspects of the disclosure may be understood through one ormore Example embodiments.

Example 1 can include or use subject matter (such as an apparatusincluding a processor configured to perform acts, a method, a means forperforming acts, or a device readable memory including instructionsthat, when performed by the device, can cause the device to performacts), such as can include or use electrical contacts, two quantum dotsembedded in a semiconductor such that when an electrical bias is appliedto the electrical contacts, an electric field produced by the electricalbias is substantially parallel to an axis through the two quantum dots,and a phononic wave guide coupled to the semiconductor, the phononicwave guide configured to transport a phonon therethrough.

Example 2 can include or use, or can optionally be combined with thesubject matter of Example 1, to include or use a lead configured toprovide excitation energy to the semiconductor, wherein the lead is anoptical lead, an electrical lead, or a phononic lead.

Example 3 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-2, to include or usewherein an electric field line of the electric field is coaxial with theaxis through the two quantum dots.

Example 4 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-3, to include or usewherein the phonon is coherent and non-dissipative in the presence ofthe electric field.

Example 5 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-4, wherein the phonon iscoherent and non-dissipative depending on presence or absence of theelectric field.

Example 6 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-5, wherein the phonon islocalized in a quantum dot of the two quantum dots dependent on theapplied electric field.

Example 7 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-6, to include or usewherein the two quantum dots are spaced apart so as to create a polaronand an indirect exciton in the presence of the electric field.

Example 8 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-7, to include or usewherein the two quantum dots include a first and second quantum dot,wherein the first quantum dot and the semiconductor provide a continuumstate, wherein the second quantum dot provides a discrete state, whereinthe continuum state and the discrete state are coupled when theelectrical bias is applied to the electrical contacts, and wherein theelectrical bias provides a gating mechanism for the coupling such thatwhen the electrical bias includes a first electro potential the electricfield inhibits the generation or transmission of phonons and when theelectrical bias includes a second electro potential different from thefirst electro potential, the electrical field promotes the generation ortransmission of phonons.

Example 9 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 1-8, to include or usewherein a phonon emitted through the phononic waveguide is determined bythe electric field.

Example 10 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 2-9, wherein a number ofphonons transported or generated can be adjusted by adjusting excitationenergy, spectral width, power density, coherence of the excitationenergy, or duration of the excitation energy.

Example 11 can include or use subject matter (such as an apparatusincluding a processor configured to perform acts, a method, a means forperforming acts, or a device readable memory including instructionsthat, when performed by the device, can cause the device to performacts), such as can include or use arranging a pair of quantum dotswithin a semiconductor such that quantum states of the pair of quantumdots resonate in the presence of an electric field, and coupling aphononic wave guide to the semiconductor.

Example 12 can include or use, or can optionally be combined with thesubject matter of Example 11, to include or use coupling an optical,electrical, or phononic lead to the semiconductor.

Example 13 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 11-12, to include or usewherein arranging the two quantum dots includes situating a firstquantum dot material horizontally adjacent to a second quantum dotmaterial using a site controlled growth technique.

Example 14 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 11-12, to include or usewherein arranging the two quantum dots includes situating a firstquantum dot material over a substrate of the semiconductor so as to forma first quantum dot of the pair of quantum dots and situating a secondquantum dot material over the first quantum dot material so as to form asecond quantum dot of the pair of quantum dots.

Example 15 can include or use, or can optionally be combined with thesubject matter of Example 14, to include or use situating a layer ofintrinsic material over the semiconductor substrate, wherein the firstand second quantum dot material are separated by the layer of intrinsicsemiconductor material.

Example 16 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 11-15, to include or usewherein the first quantum dot material includes indium arsenide.

Example 17 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 15-16, to include or usewherein the intrinsic semiconductor material includes gallium arsenideor other intrinsic semiconductor.

Example 18 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 15-17, to include or usewherein the intrinsic semiconductor material separates the first andsecond quantum dot material by less than one hundred nanometers.

Example 19 can include or use subject matter (such as an apparatusincluding a processor configured to perform acts, a method, a means forperforming acts, or a device readable memory including instructionsthat, when performed by the device, can cause the device to performacts), such as can include or use a means for providing excitationenergy, a phonon transistor coupled to the means for providingexcitation energy. The phonon transistor can include (1) an electricallyconductive medium, (2) first and second electrically conductive elementselectrically coupled to the electrically conductive medium, the firstand second electrically conductive elements configured to provide anelectric potential to the electrically conductive medium when theelectric potential is applied to the first and second conductiveelements, (3) first and second quantum dots embedded in the electricallyconductive medium such that in the presence of an electric fieldprovided by the electric potential, a state of the first quantum dotcouples with a state of a combination of the second quantum dot and theelectrically conductive medium, (4) a lead element coupled to the meansfor providing excitation energy, the lead element configured to providethe excitation energy to the electrically conductive medium, or (5) afirst phononic wave guide coupled to the electrically conductive medium,the phononic wave guide configured to transport phonons generated withinthe electrically conductive medium.

Example 20 can include or use, or can optionally be combined with thesubject matter of Example 19, to include or use wherein the means forproviding excitation energy includes a laser and wherein the leadelement includes an optical fiber.

Example 21 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 19-20, to include or usewherein the means for providing excitation energy includes an electricalpower supply and the lead element includes a wire.

Example 22 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 19-21, to include or usewherein the lead element includes a second phononic wave guide.

Example 23 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 19-22, to include or usewherein the electric field is substantially parallel to an axis throughthe first and second quantum dots.

Example 24 can include or use, or can optionally be combined with thesubject matter of at least one of Examples 19-23, wherein theelectrically conductive medium includes a semiconductor diode.

Example 25 can include of use, or can optionally be combined with thesubject matter of at least one of Examples 19-24, wherein the first andsecond quantum dots are encapsulated in an electrically insulatingmaterial that is configured to shield the first and second quantum dotsfrom direct contact with the electrically conductive medium.

Although an overview of the subject matter has been described withreference to specific embodiments, various modifications and changes maybe made to these embodiments without departing from the broader spiritand scope of the present disclosure.

The embodiments illustrated herein are described in sufficient detail toenable those skilled in the art to practice the teachings disclosed.Other embodiments may be used and derived therefrom, such thatstructural and logical substitutions and changes may be made withoutdeparting from the scope of this disclosure. The Detailed Description,therefore, is not to be taken in a limiting sense, and the scope ofvarious embodiments is defined only by the appended claims, along withthe full range of equivalents to which such claims are entitled.

Moreover, plural instances may be provided for resources, operations, orstructures described herein as a single instance. Additionally,boundaries between various resources, items with reference numbers, oroperations, are somewhat arbitrary, and particular operations areillustrated in a context of specific illustrative configurations. Otherallocations of functionality are envisioned and may fall within a scopeof various embodiments of the present invention. In general, structuresand functionality presented as separate resources in the exampleconfigurations may be implemented as a combined structure or resource.Similarly, structures and functionality presented as a single resourcemay be implemented as separate resources.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, composition, formulation, or process that includes elements inaddition to those listed after such a term in a claim are still deemedto fall within the scope of that claim. Moreover, the terms “first,”“second,” and “third,” etc. are used merely as labels, and are notintended to impose numerical requirements on their objects.

As used herein, a “-” (dash) used when referring to a reference numbermeans “or”, in the non-exclusive sense discussed in the previousparagraph, of all elements within the range indicated by the dash. Forexample, 103A-B means a nonexclusive “or” of the elements in the range{103A, 103B}, such that 103A-103B includes “103A but not 103B”, “103Bbut not 103A”, and “103A and 103B”.

These and other variations, modifications, additions, and improvementsfall within a scope of the inventive subject matter as represented bythe appended claims. The specification and drawings are, accordingly, tobe regarded in an illustrative rather than a restrictive sense.

What is claimed is:
 1. A phonon transistor comprising: electricalcontacts; two quantum dots embedded in a semiconductor such that when anelectrical bias is applied to the electrical contacts, an electric fieldproduced by the electrical bias is substantially parallel to an axisthrough the two quantum dots, wherein the two quantum dots include afirst and second quantum dot, wherein the first quantum dot and thesemiconductor provide a continuum state, wherein the second quantum dotprovides a discrete state, wherein the continuum state and the discretestate are coupled when the electrical bias is applied to the electricalcontacts, and wherein the electrical bias provides a gating mechanismfor the coupling such that when the electrical bias includes a firstelectro potential the electric field inhibits the generation ortransmission of phonons and when the electrical bias includes a secondelectro potential different from the first electro potential, theelectrical field promotes the generation or transmission of phonons; anda phononic wave guide coupled to the semiconductor, the phononic waveguide configured to transport phonons therethrough.
 2. The phonontransistor of claim 1, further comprising: a lead configured to provideexcitation energy to the semiconductor, wherein the lead is an opticallead, an electrical lead, or a phononic lead.
 3. The phonon transistorof claim 1, wherein an electric field line of the electric field iscoaxial with the axis through the two quantum dots.
 4. The phonontransistor of claim 1, wherein the phonon is localized in the quantumdots as a function of the electric field.
 5. The phonon transistor ofclaim 4, wherein the two quantum dots are spaced apart so as to create apolaron and an indirect exciton in the presence of the electric field.6-14. (canceled)
 7. The phonon transistor of claim 1, wherein a phononemitted through the phononic waveguide is determined by the electricfield.
 15. A phonon control system comprising: a means for providingexcitation energy; a phonon transistor coupled to the means forproviding excitation energy, the phonon transistor comprising: anelectrically conductive medium; first and second electrically conductiveelements electrically coupled to the electrically conductive medium, thefirst and second electrically conductive elements configured to providean electric potential to the electrically conductive medium when theelectric potential is applied to the first and second conductiveelements; first and second quantum dots embedded in the electricallyconductive medium such that in the presence of an electric fieldprovided by the electric potential, a state of the first quantum dotcouples with a state of a combination of the second quantum dot and theelectrically conductive medium; a lead element coupled to the means forproviding excitation energy, the lead element configured to provide theexcitation energy to the electrically conductive medium; and a firstphononic wave guide coupled to the electrically conductive medium, thefirst phononic wave guide configured to transport phonons generatedwithin the electrically conductive medium.
 16. The system of claim 15,wherein the means for providing excitation energy includes a laser andwherein the lead element includes an optical fiber.
 17. The system ofclaim 15, wherein the means for providing excitation energy includes anelectrical power supply and the lead element includes a wire.
 18. Thesystem of claim 15, wherein the lead element includes a second phononicwave guide.
 19. The system of claim 15, wherein the electric field issubstantially parallel to an axis through the first and second quantumdots.
 20. The system of claim 15, wherein the electrically conductivemedium includes a semiconductor diode.